7,889 research outputs found
Timelike and spacelike hadron form factors, Fock state components and light-front dynamics
A unified description of spacelike and timelike hadron form factors within a
light-front model was successfully applied to the pion. The model is extended
to the nucleon to study the role of pair production and of
nonvalence components in the nucleon form factors. Preliminary results in the
spacelike range are presented.Comment: 4 pages, espcrc1.sty. proceedings of FB XVIII (August 2006, Brazil),
to be published in Nucl. Phys.
Electromagnetic Hadron Form Factors and Higher Fock Components
Investigation of the spacelike and timelike electromagnetic form factors of
hadrons, within a relativistic microscopical model characterized by a small set
of hypothesis, could shed light on the components of hadron states beyond the
valence one. Our relativistic approach has been successfully applied first to
the pion and then the extension to the nucleon has been undertaken. The pion
case is shortly reviewed as an illustrative example for introducing the main
ingredients of our approach, and preliminary results for the nucleon in the
spacelike range are evaluated.Comment: 8 pages, 6 figs, espcrc1.sty included. Proceedings of Fifth
International Conference on Perspectives In Hadronic Physics, ICTP, May
22-26, 200
Electromagnetic form factors of the nucleon in spacelike and timelike regions
An approach for a unified description of the nucleon electromagnetic form
factors in spacelike and timelike regions is presented. The main ingredients of
our model are: a Mandelstam formula for the matrix elements of the nucleon
electromagnetic current; a 3-dimensional reduction of the problem on the
Light-Front performed within the so-called {\tt Propagator Pole Approximation}
({\bf PPA}), which consists in disregarding the analytical structure of the
Bethe-Salpeter amplitudes and of the quark-photon vertex function in the
integration over the minus components of the quark momenta; a dressed
photon vertex in the channel, where the photon is described by its
spin-1, hadronic component.Comment: 8 pages, 9 figs., macro added. Proceedings of the XI Conf. on
Problems in Theoretical Nuclear Physics, Cortona, Oct. 11-14, 200
The ionizing sources of luminous compact HII regions in the RCW106 and RCW122 clouds
Given the rarity of young O star candidates, compact HII regions embedded in
dense molecular cores continue to serve as potential sites to peer into the
details of high-mass star formation. To uncover the ionizing sources of the
most luminous and compact HII regions embedded in the RCW106 and RCW122 giant
molecular clouds, known to be relatively nearby (2-4 kpc) and isolated, thus
providing an opportunity to examine spatial scales of a few hundred to a
thousand AU in size. High spatial resolution (0.3"), mid-infrared spectra
(R=350), including the fine structure lines [ArIII] and [NeII], were obtained
for four luminous compact HII regions, embedded inside the dense cores within
the RCW106 and RCW122 molecular cloud complexes. At this resolution, these
targets reveal point-like sources surrounded by nebulosity of different
morphologies, uncovering details at spatial dimensions of <1000AU. The
point-like sources display [ArIII] and [NeII] lines - the ratios of which are
used to estimate the temperature of the embedded sources. The derived
temperatures are indicative of mid-late O type objects for all the sources with
[ArIII] emission. Previously known characteristics of these targets from the
literature, including evidence of disk or accretion suggest that the identified
sources may grow more to become early-type O stars by the end of the star
formation process
"Improving the legitimacy of medicines funding decisions: A critical literature review"
Many healthcare systems globally provide publicly subsidised access to prescribed medicines. Decisions about which medicines to fund affect a range of stakeholders and it is not reasonable to expect that medicines funding decisions are supported by all stakeholder groups all the time. A more realistic aim may be for decisions to be understood and accepted as legitimate by stakeholders, however several shortcomings of existing processes make it difficult to achieve this aim. To date, the main strategy to address these shortcomings has been to increase stakeholder involvement in decision-making, either by eliciting stakeholder values or increasing stakeholder participation in decision-making. Despite these efforts, there is growing evidence that decision-makers are falling short when it comes to the perceived legitimacy of their resource allocation processes and decisions. As such, there is a pressing need for decision-makers to think seriously and creatively about ways to increase the legitimacy of their processes and to make them more acceptable to a wider range of stakeholders. In this article we summarise and critique existing literature on the legitimacy of public resource allocation processes, and make some practical suggestions for those who are concerned about this issue. Keywords: pharmaceutical funding decisions, legitimacy, stakeholder engagement, resource allocation, priority setting.NHMR
Detection of the Vortex Dynamic Regimes in MgB2 by Third Harmonic AC Susceptibility Measurements
In a type-II superconductor the generation of higher harmonics in the
magnetic response to an alternating magnetic field is a consequence of the
non-linearity in the I-V relationship. The shape of the current-voltage (I-V)
curve is determined by the current dependence of the thermal activation energy
U(J) and is thus related to the dynamical regimes governing the vortex motion.
In order to investigate the vortex dynamics in MgB2 bulk superconductors we
have studied the fundamental (chi1) and third (chi3) harmonics of the ac
magnetic susceptibility. Measurements have been performed as a function of the
temperature and the dc magnetic field, up to 9 T, for various frequencies and
amplitudes of the ac field. We show that the analysis of the behaviour in
frequency of chi3(T) and chi3(B) curves can provide clear information about the
non-linearity in different regions of the I-V characteristic. By comparing the
experimental curves with numerical simulations of the non-linear diffusion
equation for the magnetic field we are able to resolve the crossover between a
dissipative regime governed by flux creep and one dominated by flux flow
phenomena.Comment: to be published in "Horizons in Superconductivity Research" (Nova
Science Publishers, Inc., NY, 2003
The distribution of oxygen at the Ni81Fe19/Ta interface
The knowledge of how oxygen atoms are distributed at a magnetic-metal /
oxide, or magnetic-metal / non-magnetic-metal interface, can be an useful tool
to optimize device production. Multilayered Ni81Fe19 / Ta samples consisting of
15 bilayers of 2.5 nm each, grown onto glass substrates by magnetron sputtering
from Ni81Fe19 and Ta targets, have been investigated. X-ray absorption near
edge structure, extended X-Ray absorption fine structure, small angle X-ray
diffraction, and simulations, were used to characterize the samples. Oxygen
atoms incorporated onto Ni81Fe19 films during O2 exposition are mainly bonded
to Fe atoms. This partial oxidation of the Ni81Fe19 surface works as a barrier
to arriving Ta atoms, preventing intermixing at the Ni81Fe19 / Ta interface.
The reduction of the Ni81Fe19 surface by the formation of TaO x is observed.Comment: 14 pages, 9 figures, accepted for publication in Advances in
Materials Science and Engineerin
Beta defensin-2 is reduced in central but not in distal airways of smoker COPD patients
Background: Altered pulmonary defenses in chronic obstructive pulmonary disease (COPD) may promote distal airways bacterial colonization. The expression/activation of Toll Like receptors (TLR) and beta 2 defensin (HBD2) release by epithelial cells crucially affect pulmonary defence mechanisms. Methods: The epithelial expression of TLR4 and of HBD2 was assessed in surgical specimens from current smokers COPD (s-COPD; n = 17), ex-smokers COPD (ex-s-COPD; n = 8), smokers without COPD (S; n = 12), and from non-smoker non-COPD subjects (C; n = 13). Results: In distal airways, s-COPD highly expressed TLR4 and HBD2. In central airways, S and s-COPD showed increased TLR4 expression. Lower HBD2 expression was observed in central airways of s-COPD when compared to S and to ex-s-COPD. s-COPD had a reduced HBD2 gene expression as demonstrated by real-time PCR on micro-dissected bronchial epithelial cells. Furthermore, HBD2 expression positively correlated with FEV1/FVC ratio and inversely correlated with the cigarette smoke exposure. In a bronchial epithelial cell line (16 HBE) IL-1β significantly induced the HBD2 mRNA expression and cigarette smoke extracts significantly counteracted this IL-1 mediated effect reducing both the activation of NFkB pathway and the interaction between NFkB and HBD2 promoter. Conclusions: This study provides new insights on the possible mechanisms involved in the alteration of innate immunity mechanisms in COPD. © 2012 Pace et al
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